Science of Catch and Release, an Introduction by: David Coulson   10/1/2009

I enjoy reading fishing articles and books, not only the standard fare sold at tackle shops, but also scientific journals and texts. A recent article caught my eye, “A review of catch-and-release angling mortality with implications for no-take reserves”, by Aaron Bartholomew & James A. Bohnsack, published in Fish Biology and Fisheries (2005).

So, what is the problem with catch and release (C&R) fishing in “no-take reserves”?  The fish are released to fight another day, right? It turns out things are not clear cut. The authors concluded that C&R fishing was incompatible with “no take” reserves as an unacceptably large number of fish could potentially be killed.  They based their conclusion on the review of numerous C&R studies that showed, depending on fishing methods and species, total morality(initial and post) due to C&R averaged 18 %, ranging from less than 1% to over 80%.

Since that article, I’ve collected and read many more on C&R. And I’ve only touch the tip of the iceberg. One meta-analysis (a scientific review of articles) from 1950 through 2008 found over 260 published scientific studies on C&R fishing.

Being a C&R fisher myself, the biggest surprise was that catch and release fishing is not benign.  The evidence is overwhelming that not every fish released will survive to fight another day.  Regardless of the fishing method and species, there will be some post-mortality (fish swims away and dies later) with released fish. 

So a few fish die, what’s the big deal?  With healthy fisheries, it probably isn’t.   However, given everyone who fishes in Colorado practices C&R to some degree (releasing undersized fish, undesirable species, fish outside size limits, etc), mortality from C&R may impact a fishery.

All public waters and most species have some limit on take (number of fish we can kill).  Catch and release fishing isn’t limited, in part because we assume released fish will live to fight another day.  Sounds good, but the evidence is irrefutable, some released fish will die in the process. It’s just a matter of how many. 

Consider a lake with a limit of two trout and no restrictions on fishing methods.  Now assume that the average post-mortality for trout (all methods) is 10%.  I go fishing, set out a baited line and throw spinners (or flies) on a second rod and fish all day.  Being conservation minded I opt to release everything I can.  It turns out I have a great day, and keep my limit and release another 20 fish.  Meaning, I possibly killed another two fish beyond my limit.  So I may have unintentionally “harvested” twice my limit. For those smug fly fishers (like me) the story is the same. Even if your post-mortality rate is lower than the average fisher and you release everything, some fish will die.  Thus, it is possible for you kill more fish than the legal limit on any given day. 

I feel that as fishers we need to recognize our fishing activities, including C&R, do impact our fisheries.  Since we all practice C&R some degree, understanding and using “best” practices from a scientific perspective seems prudent.  To that end, over the next few blogs I’ll delve deeper into the “best” C&R practices concept based on scientific literature.  

Member comments

by: HeavyC on 10/1/2009 2:28:43 PM
Interesting Dave I am looking forward to your updates!!! HC Out!

 

by: BITE ME on 10/1/2009 2:47:31 PM
interesting and a big eye opener, Two side to everything in life

 

by: Dan Swanson on 10/1/2009 4:13:53 PM
So if the limit is 2, you should keep the first 2 fish you catch and go home? Or catch 20 and keep none. I'm looking forward to what you find. I hope it's species specific on the delayed mortality stats as well as take into account things like water temperature, lip hooked, throat hooked, gill hooked, hook left in the fish and the line cut, mishandled in some way, etc.

 

by: ronnycast on 10/1/2009 6:55:17 PM
Other things that should be noted like depth the fish were caught, line and rod weights that may contribute to long or extended fish playing, break offs due to thing like fishing with too light of line so as to leave fish swimming around with lures in their faces, miss handling of fish during the catch or after the catch like dropped fish, fish that weren’t allowed to breath and catch there breaths before being measured photographed and weighed and countless other thing that might skew the statistics. I do know one thing, if it's put on ice it has zero chance of living.

 

by: Good Sam on 10/1/2009 7:37:06 PM
I'm very interested to see more about this.

 

by: Flyrodn on 10/2/2009 9:36:02 AM
There will be a lot to cover as "Best" practices do require consideration as to bait/lure, water temp, hook type, remove vs leave hook, water depth, preditor level, handling, nets, air exposure, equipment type, retention time/method (live wells, species, fish size, fisher's skill/experience level. Concerning what do you do if you practice C&R and suspect you have reached or exceeded the limit on the water? Little doubt in my mind you're legally allowed to fish. But ethically, that's not so clear cut. If the limits are there as a management tool, to maintain the fishery, it would seem ethically we should quit for the day. If limits are just a way of forcing folks to share, maybe not. The example was meant to get folks thinking about the issue. As high levels of fishing pressure, even with C&R could possibly have a negatively impact a fishery, it is possible in my mind, that it would be approriate to ask folks to quit fishing on a specific water after releasing some number of fish. So in my example, my opinion is once you reached your "kill" limit of two trout be it by retaining or releasing, ethically, you should quit for the day for that species on that water. Hard to do, and frankly, I don't practice what I've just suggested, but I'm giving it a lot of thought and consideration.

 

by: Jim2007 on 11/7/2009 5:35:54 PM
Hi Dave: Great blog. I am a C&R guy. I use flies most of the time on a spinning rod. The hook always comes out. The Colorado Division of wildlife is telling us that if you use bait and gut hook the fish it is ok to just cut the line and the hook will rust out in time. I did net a R. Trout that had a line and hook in it. It was in bad shape and skinney. I think the Division of wildlife is wrong in recommending the release of fish that still have a hook in them. Jim2007

 

by: brookieflyfisher on 11/7/2009 6:14:12 PM
Jim2007, I'm going to have to disagree. I've caught plenty of fish with hooks still in them, and the vast majority have been healthy, and one even had the hook and line coming out the other end. I've also hooked and landed fish that had lures in their mouths with the hooks rusting away. I've actually had a fish regurgitate a rusted hook when I caught it, and it was a healthy fish. So in most cases I believe the cut the line system to be a good alternative. Just sharing my experiences.